The T-TEST procedure outputs tables used in testing hypotheses about
means.
It operates in one of three modes:

One Sample mode.

Independent Groups mode.

Paired mode.

Each of these modes are described in more detail below.
There are two optional subcommands which are common to all modes.

The /CRITERIA subcommand tells PSPP the confidence interval used
in the tests. The default value is 0.95.

The MISSING subcommand determines the handling of missing
variables.
If INCLUDE is set, then user-missing values are included in the
calculations, but system-missing values are not.
If EXCLUDE is set, which is the default, user-missing
values are excluded as well as system-missing values.
This is the default.

If LISTWISE is set, then the entire case is excluded from analysis
whenever any variable specified in the /VARIABLES, /PAIRS or
/GROUPS subcommands contains a missing value.
If ANALYSIS is set, then missing values are excluded only in the analysis for
which they would be needed. This is the default.